Search

High thermal stability is of pivotal significance for hole transport materials (HTMs) owing to thermal evaporation and device operation stability requirements. In this study, two new HTMs, namely FCzTPA and FCzDPNA, were developed by using easily accessible carbazole/dibenzo[b,d]furan derivatives. The rigid structures bring about excellent thermal stability, with a decomposition temperature (Td) of up to 400 °C and glass transition temperature (Tg) above 190 °C. Moreover, benefiting from the twisted spatial configuration and constituent units, they both exhibit suitable triplet energy levels (ET = 2.56, 2.74 eV). When hosting red phosphorescent organic light emitting diodes (PhOLEDs), the FCzTPA-based device shows a turn-on voltage (Von) of 3.4 V and the maximum external efficiency (EQEmax) of 18.61%, indicating that the synthetic compounds are potential building blocks for highly efficient OLEDs. [ABSTRACT FROM AUTHOR]

Full colour display is vital to organic lighting-emitting diodes (OLEDs) and universal hosts for all red, green and blue (RGB) OLEDs are strongly desired. In this work, a universal bipolar host, namely BCz3PhCN, was synthesized by simply incorporating carbazole and isonicotinonitrile units. BCz3PhCN exhibits excellent thermal stability and a high triplet energy level (ET) of 2.76 eV; therefore, all RGB devices were fabricated to evaluate their electroluminescent (EL) performance. The blue device hosted by BCz3PhCN was lit at 3.0 V with the maximum external quantum efficiency (EQEmax) of 16.22%. Green PhOLEDs exhibited a better performance with the maximum luminance (Lmax) of 1 21 900 cd m−2, maximum current efficiency (ηc,max) of 69.30 cd A−1, maximum power efficiency (ηp,max) of 64.88 lm W−1 and EQEmax of 20.04%. Remarkably, the highest EQEmax of 26.84% was achieved by the red device in the low luminance range. The above excellent EL performance for all BCz3PhCN-based blue, green and red devices indicates a huge potential for BCz3PhCN as a universal host in developing high-performance monochrome and white OLEDs. [ABSTRACT FROM AUTHOR]

Two new organic small molecules composed of phenanthrene, carbazole and an electron deficient moiety were synthesized by a Suzuki coupling reaction. It is particularly intriguing to compare the electroluminescent (EL) properties of PBBM and PBTZ, which have the same molecular structure with the respective high Td at around 436 °C and 423 °C. By changing the electron deficient moiety of the C9-position of phenanthrene, the photophysical, electrochemical and electroluminescent properties of these two compounds showed significant differences. Furthermore, green and red phosphorescent organic light emitting diodes (OLEDs) employing PBBM and PBTZ as host materials exhibited low efficiency roll-off, and the red OLEDs based on both compounds revealed better EL performance than those of the green OLEDs. Especially, the PBBM-hosted green and red OLEDs achieved a maximum EQE of 14.3% and 18.2%, respectively. [ABSTRACT FROM AUTHOR]

Abstract In this work, two host materials, 9-(4-(7-(9,9'-spirobi[fluoren]−2-yl)-[1,2,4]triazolo[1,5- a ]pyridin-2-yl)phenyl)−9H-carbazole (CzTPSp1) and 9-(4-(6-(9,9'-spirobi[fluoren]−2-yl)-[1,2,4]triazolo[1,5- a ]pyridin-2-yl)phenyl)−9H-carbazole (CzTPSp2) were designed and synthesized by utilizing carbazole as hole-transport units and [1,2,4]triazolo[1,5- a ]pyridine (TP) as electron-transport units. These two compounds exhibit good thermal stability, appropriate frontier orbital energy levels, high triplet energy levels, and balanced carrier transport properties. Red phosphorescent organic light-emitting devices (PhOLEDs) based on these two hosts and bis(1-phenylquinoline) (acetylacetonate)iridium (III) (Ir(pq) 2 acac) exhibit satisfactory efficiencies with the maximum external quantum efficiency (η ext, max) of 23.0% and 22.1%. To our knowledge, among the red-emitting OLEDs based on Ir(pq) 2 acac, the η ext, max (23.0%) of our device is the highest reported so far. Meanwhile, efficiency roll-off in these devices are far less obvious, at the luminance of 1000 cd m−2, the η ext of devices R1 and R2 can reach to be 22.0% and 21.6% with the efficiency roll-off value of 4.3% and 2.2%. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Three bipolar hosts, 9-(4-(2,3-diphenylquinoxalin-6-yl)phenyl)-9 H -carbazole ( p -PQPC ), 9-(3-(2,3-diphenylquinoxalin-6-yl)phenyl)-9 H -carbazole ( m -PQPC ) and 9-(2-(2,3-diphenylquinoxalin-6-yl)phenyl)-9 H -carbazole ( o -PQPC ) were designed, synthesized and characterized for red phosphorescence organic light emitting devices (PhOLEDs). These three compounds exhibited excellent physical properties with high thermal stabilities, reasonable HOMO-LUMO energy levels and balanced charge transport. All of them were applied to fabricate red PhOLEDs as host materials, and the p -PQPC based device demonstrated outstanding electroluminescence performance with the maximum current efficiency, power efficiency and external quantum efficiency of 21.9 cd/A, 15.4 lm/W and 12.2%, respectively, which suggesting that p -PQPC is a promising host for red PhOLEDs. [ABSTRACT FROM AUTHOR]

Two host materials based on spiro[fluorene-9,8′-indolo[3,2,1- de ]acridine] derivatives were designed and synthesized by introducing the benzofuran/benzothiophene unit to the spiro [fluorene-9,8′-indolo[3,2,1- de ]acridine] unit. The two host materials exhibited high triplet energy level (> 2.65 eV) and the benzofuran-substituted derivative presented suitable glass transition temperature (> 130 °C). Their electrochemical and photo-physical properties were also determined. The green phosphorescent organic light-emitting diodes based on the two host materials obtained electroluminescence performances with external quantum efficiencies of 14.3 ± 0.1% and 11.9 ± 0.1%, respectively. [ABSTRACT FROM AUTHOR]

We report two bipolar host materials bearing hole-transport benzofurocarbazole/indenocarbazole cores and an electron-transport benzimidazole moiety for red phosphorescence organic light emitting devices (PhOLEDs). The two novel host materials exhibited excellent physical properties with high thermal stabilities, appropriate HOMO-LUMO energy levels and balanced charge transport. Both of them were applied to fabricate red PhOLEDs as promising host materials, and 7,7-dimethyl-5-(4′-(1-phenyl-1 H -benzo[ d ]imidazol-2-yl)-[1,1′-biphenyl]-4-yl)-5,7-dihydroindeno[2,1- b ]carbazole ( ICBI ) based device demonstrated outstanding electroluminescence performance with the maximum current efficiency, power efficiency and external quantum efficiency of 33.0 cd/A, 13.9 lm/W and 18.9%, respectively. [ABSTRACT FROM AUTHOR]

Three novel molecules were designed and synthesized based on a known compound 9,10-di(naphthalen-2-yl)anthracene (MADN). To broaden the π-conjugated system, three units with different electronegativity were introduced and connected to the C-2 position of MADN by vinyl unit. The Suzuki reaction, the Wittig reaction, and the Heck reaction were employed to synthesize these compounds. MADN is a well-known anthracene derivative which has been widely used as blue emitter. All these results indicate that these novel MADN derivatives could be some kind of potential materials for OLEDs. [ABSTRACT FROM AUTHOR]

A new bipolar host material based on triphenylamine, fluorene and 1,2-diphenyl-1 H -benzo[ d ]imidazole moieties, N , N -diphenyl-4-(9-phenyl-2-(4-(1-phenyl-1 H -benzo[ d ]imidazol-2-yl)phenyl)-9 H -fluoren-9-yl)aniline (DPPBIPFA), was designed and synthesized. The as-synthesized material was well characterized by 1 H and 13 C NMR spectroscopy, high-resolution mass spectrometry and thermogravimetric analysis, respectively. The photophysical and electrochemical properties of the material were also studied. The material exhibited an excellent thermal stability ( T d = 475 °C), electrochemical stability and high triplet energy (2.68 eV). A green phosphorescent organic light-emitting diode (PhOLED) device based on DPPBIPFA as the host material and Ir(ppy) 3 as the dopant was fabricated, which displayed favorable electrophosphorescent properties with a turn-on voltage of 3.75 V, a maximum brightness of 1685 cd/m 2 and a maximum current efficiency of 4.26 cd/A. [ABSTRACT FROM AUTHOR]

Two novel host materials based on 5- and 9-substituted benzocarbazole have been developed for application in phosphorescent organic light-emitting diodes. Both host materials exhibit excellent thermal stability with high decomposition temperatures of ca.515 °C, while the 9-substituted benzocarbazole derivative exhibits a high glass transition temperature of 181 °C. Additionally, the electroluminescence characteristics of green phosphorescent organic light-emitting diodes made with two new host materials were also evaluated. The devices exhibited an electroluminescent emission peak at 528 nm with CIE coordinates of (0.31, 0.64) and possessed low turn-on voltages of <2.84 V. [ABSTRACT FROM AUTHOR]

In this work, by introducing triphenylvinyl group to the backbone of N , N -diaryl fluorenamine, three novel hole transport materials (HTMs), namely TFlA-BP , TFlA-Fl and TFlA-Nap , were designed and synthesized. These materials exhibit excellent thermal stability, high triplet energy levels (E T), appropriate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels. Double layer green OLEDs with TFlA-BP , TFlA-Fl and TFlA-Nap as hole transport layer (HTL) show good electroluminescence (EL) performance with the maximum power efficiencies (η p) and external quantum efficiency (EQE) of 3.40 lm W−1/1.29%, 3.12 lm W−1/1.35% and 3.15 lm W−1/1.29%, respectively, which are comparable to that of the NPB-based one (2.63 lm W−1/1.36%). [Display omitted] • Three novel HTMs based on triphenylvinyl substituted N , N -diaryl fluorenamine were presented. • All the materials exhibited excellent thermal stability, appropriate HOMO/LUMO and E T levels. • Devices employing them as HTL exhibited comparable EL performances compared to that of the NPB-based one. [ABSTRACT FROM AUTHOR]

In this research, a novel macrocycle containing tetrabenzeneaza has been developed as a novel building block for hole transport materials (HTMs). Benefiting from its unique highly twisted spatial configuration, this macrocycle exhibits high triplet energy level (E T) as well as high hole mobility. Based on this aza macrocycle, two hole transporting materials, namely 2TPATPCA and 2CzTPCA , were designed and synthesized. Both 2TPATPCA and 2CzTPCA possess enough E Ts, appropriate frontier orbital energy levels as well as good thermal stability, which promote them as universal HTMs in multicolor phosphorescent organic light-emitting devices (PhOLEDs) and thermal activated delay fluorescence (TADF) OLEDs. High external quantum efficiencies (EQEs) were realized in OLEDs using the these two HTMs. For example, sky bule PhOLED with 2CzTPCA showed a significantly improved maximum EQE of 20.3% compared to that of the reference device using N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) (EQE of 14.2%) and 4,4′-Cyclohexylidenebis[N,N- bis(4-methyl phenyl)aniline (TAPC) (EQE of 12.2%). Green TADF OLED using 2CzTPCA as HTM also exhibit a much improved maximum EQE of 17.9% compared to that of the reference device based on NPB (EQE of 10.3%). These results indicate this tetrabenzeneaza macrocyclic is a promising building block for developing universal high-performance HTMs. Image 1 • Developed a novel platform – tetrabenzenacyclohexaphane for building HTMs. • Tetrabenzenacyclohexaphane derivatives exhibited high triplet energies, good thermal stability, and high hole-transporting abilities. • Universal HTMs based on tetrabenzenacyclohexaphane in multicolor PhOLEDs and TADF OLEDs exhibited superior performance. [ABSTRACT FROM AUTHOR]

In this paper, three novel bipolar host materials, 9,9′-Diphenyl-6-(4-pyridinyl)-3,3′-bicarbazole(BCz4Py), 9,9′-Diphenyl-6-(3-pyridinyl)-3,3′-bicarbazole(BCz3Py) and 9,9′-Diphenyl-6-(5-pyrimidinyl)-3,3′-bicarbazole(BCz5Pm), were synthesized by incorporation of bicarbazole as donor with pyridine/pyridimide based N-hexahydroxy nitric heterocycle as acceptor units. The photophysical, thermal and electrochemical properties of these three materials were fully investigated. These compounds all exhibited superior thermal stability with high glass-transition temperature (T g > 130 °C) and decomposition temperature (T d > 400 °C). Appropriate HOMO (highest occupied molecular orbitial) -LUMO (lowest unoccupied molecular orbital) levels and triplet energy (2.74–2.75 eV) of these compounds make them suitable hosts for green iridium pohosphor Ir(ppy) 3 in phosphorescent organic light emitting devices (PhOLEDs). Among them, the BCz3Py hosted device exhibited outstanding performance with maximum external quantum efficiency (EQE) of 14.9%, maximum current efficiency (CE) of 49.9 cd/A, and maximum power efficiency (PE) of 29.1 lm/W, suggesting that BCz3Py is a promising bipolar material for high-efficiency green PhOLEDs. Image 1 • Three novel bipolar host materials were synthesized by incorporation of bicarbazole as donor with pyridine/pyridimide based N-hexahydroxy nitric heterocycle as acceptor units. • The synthesis and characterization of these three compounds have been carried out thoroughly. • The green OLEDs based on three compounds were systematically compared. • The performance of the device based on BCz3Py is impressive with a max EQE of 14.9%. [ABSTRACT FROM AUTHOR]